Shamanism is a technology for exploring non-ordinary states of consciousness in order to accomplish specific purposes: healing, divination, and communication with the spirit realm. The characteristics of shamanism were defined by the religious historian Mircea Eliade: "special relations with 'spirits,' ecstatic capacities permitting of magical flight, ascent to the sky, descent to the underworld, mastery over fire, etc." Shamanism can also involve magical transformation of humans into animals, prophetic dreams, and interaction with the souls of the dead.

The belief system of shamanism posits, besides the dimensions of space and time that are tangible to us, other dimensions, accessible through heightened consciousness or trance. These other dimensions, which pass through every human being, are often represented by the Axis Mundi, or World Tree, with roots reaching down into the lower domains of ghosts and spirits, and branches stretching up towards the gods. "The underworld, the center of the earth, and the "gate" of the sky are situated on the same axis, and in past times it was by this axis that passage from one cosmic region to another was effected," Eliade notes.

The phenomenon of shamanism is unfathomably old and amazingly widespread. Shamanism is a fully developed enterprise among Australian tribes who separated from other human populations as much as forty thousand years ago. Outside of the modern Western cultures, shamanism seems to be something close to a universal human phenomenon. Eliade illuminates cross-cultural similarities in shamanic belief systems across the world. From Australia to Brazil to Siberia, he documents myths of ancient "cosmic serpents" that brought life to earth, of an original battle in which the men overthrew a primordial and feminine chaos to begin time, of the healing power of rock crystals and the magic breath of the shaman.

Shamanic initiation often takes the form of a sickness - the cure is the discovery of the vocation. Eliade describes a famous Yakut shaman who had been ill as a young man: "he needed to shamanize; if he went for a long time without doing so, he did not feel well." Shamans often become sick when they are young. During their illness, they may see visions of spirits or meet the ghosts of their ancestors. Shamanism can also be inherited through a family line. A dramatic way to become a shaman is to be struck by lightning and survive. "The Greeks believed a person struck by lightning was in possession of magical powers, and in tribal cultures throughout the world lightning shamans are venerated and feared as mighty shamans," notes Holger Kalweit, a German scholar who recounts several case histories of lightning shamans who manifested superhuman powers given to them by the "Thunder Beings."

Traditionally, the evolution from ordinary human state to shaman is marked by a series of visions and dreams of the novice being killed, dismembered, eaten, regurgitated, and put back together by the spirits. His or her bones are replaced with quartz crystals, precious metals, or similar magical substances. For instance in Borneo, according to Eliade, the spirits of past shamans come to the initiate, they "cut his head open, take out his brains, wash and restore them… they plant barbed hooks on the tips of his fingers to enable him to seize the soul and hold it fast; and lastly they pierce his heart with an arrow to make him tender-hearted, and full of sympathy with the sick and suffering." In most cultures the majority of shamans are men; however, when women become shamans they are often especially powerful. In some tribes, shamans have an ambiguous gender-identity, dressing like women, or remaining celibate.

Shamanic operations utilize a substance that is produced within the shaman's body and materialized in various ways, as a fluid, rock crystal, or magical dart. According to the anthropologist Alfred Metraux: "The shaman's power also has been described by some authorities as a substance which the magician carried in his body. The gestures of shamans during their magic operations suggested that they were handling some invisible stuff which they removed from the patient's body or transmitted to persons or even things to enhance their excellence. The Apapocuva-Guarani shamans, for instance, were given a substance by the spirits which, in turn, they could communicate to other people to increase their vitality."

Some writers, such as Terence McKenna, have equated this substance with the primal substance, between matter and consciousness, sought by the alchemists. In The Hermetic Tradition, a book on the European tradition of alchemy, Julius Evola writes, "the hermeticist performs certain operations by which he actualizes and brings to perfection a symbolic "Matter."" In the symbolic language of alchemy, this precious stuff is the "gold" that the alchemists seek to fabricate. For William Irwin Thompson, the shaman, like the yogi, "is a transformer who takes in powerful energies, steps them down, and turns them into a weaker alternating current that can be used in all the homes of the ordinary folk." The shaman "can connect the human realm of consciousness with the divine and thereby preserve the integrity of the human world."

Eliade sums up the vast anthropological literature on shamanic initiations as "the death and mystical resurrection of the candidate by means of a descent to the underworld and an ascent to the sky." The candidate, while he is undergoing shamanic initiation, receives a "massive influx" of the sacred. The temporary unleashing of supernatural forces that the initiate must learn to control can be dangerous to himself and those around him.

The traditional shaman is healer, gardener, storyteller, forecaster, and initiator into the spirit realms. One of his tasks is to bring the souls of the dead to their place in the underworld. The shaman's wisdom, his relationship with the spirit realm, his capacity for ecstatic experience, makes him "the great specialist in the human soul; he alone "sees" it, for he knows its "form" and its destiny," Eliade writes.